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Name:____________________ Date:________________ Chemistry 1-6 Explore Paper Clip Patterns In this activity you will explore why measurements involve a degree of uncertainty. Materials (per student) Paper Clip Procedure 1. Measure the length of a paper clip on each ruler pictured below. The measurements will not be identical. Write your answers in the space provided. length of paper clip ______-cm length of paper clip ______-cm length of paper clip ______-cm Questions 1. Were all of your measurements identical? Explain. 2. Which measurement required the greatest amount of estimation? Explain. 3. How do your measurements indicate this difference in the degree of estimation needed? Chapter 1 32 Prentice-Hall, Inc. Name:____________________ Date:________________ Chemistry 1-6 Practice Problems Identify the number of significant digits in each of the following measurements. Write the number in the space provided. 1. 520-mL ______________ 5. 10.002-ns ______________ 2. 0.0102-ms ______________ 6. 0.451-Pa ______________ 3. 0.230-kg ______________ 7. 0.001-cm ______________ 4. 25,600-L ______________ Perform the following calculations and round off the answer to the correct number of significant digits. 8. 0.3287-g x 45.2-g =? 13. 0.258-mL + 0.36105-mL =? 9. 125.5-kg + 52.68-kg + 2.1-kg =? 14. (1250-cal - (234.207-cal ÷ 52.69-cal)) =? 10.52.8 Pa + 3.0025 Pa = ? 253.4 Pa 15. 78.26 L - 89.50 L = ? 678.2-L+9511-L 11. (0.12-g + 5.16-g) x (45.56-g - 93.0-g) = ? 12. 68.32-ns + (-1.001-ns) + (-0.00367-ns) + (-678.1-ns) = ? Chapter 1 33 Prentice-Hall, Inc. Name:____________________ Date:________________ Chemistry 1-6 Practice Problems (continued) Express each of the following numbers in scientific notation. 16. 8960 19. 36,000,000 ______________ 17. 0.00023 ______________ 20. 0.0000000253 ______________ 18. 86,000 ______________ Check the following equalities for errors. If an answer is correct, write "correct" in the space provided. If an answer is incorrect, rewrite it to make it correct. 21. 45,630,000 = 4.563 x 107 ____________________ 22. 0.000253 = 2.53 x 10-3 ____________________ 23. 680,500,000 = 68.05 x 108 ____________________ Solve each of the following problems as directed. Show all your work. 24. An unknown liquid has a mass of 30.6-g and a volume of 52.3 mL. What is the density of the liquid? 27. The density of ice is 0.917-g/cm3. How much volume does 52.3-g of ice occupy? 25. Iron has a density of 7.86-g/cm3. Could a block of metal with a mass of 18.2-g and a volume of 2.56-cm3 be Iron? Explain. 28. If 1.35-g of aluminum occupies 0.500 cm3, what is the density of Aluminum? 26. The density of Gold is 19.3-g/cm3 . What is the mass of 11.3-cm3 of Gold? Chapter 1 34 Prentice-Hall, Inc.